Hi,

I've just searched the forums and haven't found an answer - so here's a first post in hope! I'm in Suffolk, UK, and driving a 1990 LS400 that's running well after 220,000 miles!

The issue I have is that there is a constant current running when the car is switched off. It measures between 200mA and 250mA. Predictably, if the car isn't used for a few days then the battery goes completely flat and needs a charge which is irritating.

There are no obvious electrical items switched on when the car is off (I have taken out the boot light bulb to check that. I have tried taking out the fuses one at a time, but am not sure how to remove the 'large' fuses in the fusebox under the hood. However, nothing I have done has caused the current to fall back.

I wonder if anyone else has had a similar issue and solved it. Any advice or help would be gratefully received!

Thanks,

Jon

 

I've seen this before with the CD changer draining battery power. Try and unplug it for a few days, and see.

Im having the same problem on my SC (except mine goes out if left for over 30hrs), and i have not found a solution to date (changed battery of course). Search both the LS, and SC forums for more help on this topic.

 

check the courtesy light switches. Happened to me once.

 

Thanks very much for these suggestions.

I'm certain that all of the cabin lights go off when the doors are shut, so I don't think it's the courtesy light. Could this circuit drain current if the lights are off? If you think so, let me know (and which fuse to check, if you know!)

Is there a separate fuse for the CD changer? Do you know where it is? I note that the light on the CD changer goes off with the boot light (you can tell this by pressing the boot catch down while the boot is open) so this, too, may not be the problem.

I'll search the forums on these issues - but haven't turned up anything else that seems helpful yet.

Thanks again - any more suggestions gratefully received.

Jon

 

Even with the CD changer light off, it still may be draining battery power. I tell you this because I’ve read it a few times on the forums... not to mention that this problem started happening to me right when I fixed my CD changer. Try and unplug the connector going to the changer (not sure which fuse).

Also, I’ve read the pre-delivery reports for the SC that the dome lights fuse should be pulled before the car is delivered because it decreases battery drain by 45% or something close to that. Check in your owner’s manual about fuse number, and location. (don’t have mine on me.)
If you don’t have one, Lexus will send you one free of charge. Just call their 1800 number.

As you can see, it doesn’t have to be evident with lights on or such for circuits or modules to be draining battery power. It’s a very tough issue to diagnose, but a must. I will let you know if I catch any leads.

 

Check the seat adjusment switch to make sure it works properly. Mine was broken and stuck (jammed) caused the seat motor to run 'til battery ran out.

 

I have also ran across a case where the diode in the alternator had failed allowing the current to drain back through the charging circuit. Disconnecting the alternator wires should tell if it's the problem.

 

This was my first thought - but I have been told by a couple of mechanics that the current is too low (<0.5A) for this to be the issue. Apparently it would be a few amps if the alternator were to blame. However... problem's still not fixed, so who knows!

I'm trying to find out how to disconnect the CD changer, to give that option a try first - or, perhaps more simply, to identify whether the changer is on its own circuit, and which fuse I could then pull out to simply disable it.

Thanks for your input. I'll post the answer when I come up with it. In the meantime, any further ideas gratefully received.

Jon

 

Do you have an Owner's Manual? All the fuses are listed in there. According to my 91 manual fuse 4 'Radio' and fuse 20 'Dome' both supply power to the CD player.